Analog electronics

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* Diodes

* Application of diodes

* Circuit with Zener diode

* Transistor DC

* Transistor structure

* Field Effect Transistors (FET)

* The low frequency transistor

Field effect transistors *

* Amplifier generally I and II operational feedback

Considers analog electronics and works with continuous values may take infinite values, we can narrow that deals with signals that change over time because studies continuously driving states and conduction of diodes and transistors used to design computations in algebra with which integrated circuits are manufactured.

Analog electronics covers many fields such as dynamic analog electronics is a circuit that carries deep or vibration to an electrical system, the hydraulic analogue which is between a current surface water or a two-dimensional flow example a clock, which tends to tene4r different gear types which are driven by a driver to move the gears that are different sizes but each to a specific function like the seconds, minutes and hours.

We can also say that the analog electronics defines specific fields such as:

* Conducting semiconductors.

* Diodes

* Diode circuits.

* Transistor Biopolar

* Stages transistoradas.

* Field effect transistors.

* Amplification and feedback.

* Operational amplifier (I).

* Operational amplifier (II).

* Other systems amplifiers

* Other analog systems

* Active filters.


It is a discrete component that allows the current flowing between the terminals in a certain direction, whereas the opposite sense blocks,

Ideal diode Operation: The operation of the ideal diode is a component that has zero resistance to current flow in a certain direction and infinite resistance otherwise.

V = 10V, R = 1K, D = diode, i = 10 mA.

* Driving the diode in the forward direction (closed diode)

V = 10V, R = 1K, D = diode, I = 0mA.

b) Driving in reverse diode (LED open)

Junction diode:

The diode is a semiconductor element due to the function of the joints, opposite characteristics, i.e., one N-type and P-type other Both unions are junction diode (built with German materials and silicon)

We have when they are joined the two materials, the electrons and holes in the junction region are combined, resulting in a lack of carriers in the region near the junction.

Arrangement of holes – electron binding region:

There operating characteristic curve junction diode. There are three regions driving a) direct region, region and reverse breakdown region.

The junction diode operates in two such regions:

* Direct region

* Reverse region.

Diode characteristic curve:

* Condition bias. Where Ri = [V (max) – Vz] / [Iz (max) + Il (min)], substituting values Ri = [(24) – 10] / [(140) + (20)] = 87.5 Q

When considering various combinations of V and Ri we can determine that the diode current remains within the range 14 140 mA, as stated in theory.


* Design a voltage regulator, using the circuit in the previous chapter. Having Suppose that the diode has a breakdown voltage Vz = 10V, the charge current is variable 100 200 mA, the voltage source is in the range 14V 20V. Find Ri and maximum power value required Having diode.

* Design a voltage regulator using the circuit shown above. According Having diode has a breakdown voltage Vz = 9V load, this load current varies 400 800 mA, the voltage source is in the range


Responses: a) and b)


Analysis with the load line.

* Simple circuit with a diode, b) characteristic curve (Id – Vd)

Solution: Applying Kirchhoff to the circuit

E – Vd – Vr = 0 (a). E = Vp + Ip x R (b), we have that the variables (Vd, Id) are the same, there are two conditions to graph. Plotting the points on the axes. a) Having diode symbol b) Feature V – I have a diode.

Symbol of Zener diode and diode PN.

According symbols is understood driving direction together with the polarization. Some diodes are designed to exploit the reverse breakdown voltage with a characteristic curve shown above. This is achieved mainly through the control of them are achieved doped breakdown voltages of 1.8 V to 200 V and maximum outputs from 0.5 W to 50 W.

The characteristic of a Zener diode, not unlike theoretically ideal diode although employment philosophy is different, the zener diode is used to work in the rupture zone, as keeps the voltage across its terminals (zener voltage , Vz).

A very common application is the stabilization voltage. Commercial parameters are equal to normal diode, Iz (max) = maximum current in reverse. Keep in mind that the manufacturer gives the values of Vz and Iz (max) in absolute value.

When solving a problem, it must be remembered that the values are negative with the sign criteria set by the command component shown. However the zener acts in the three states.

* Direct drive (normal diode).

* Driving inverse diode (typical)

* Driving in reverse bias, V = Vz = Cte and Iz (max) is between 0 and Iz (max).


Previously we found that the breakdown voltage of a Zener diode was almost constant over a wide range of reverse bias currents. This causes the zener diode circuit is used in a voltage regulator or a voltage reference circuit, this section will deal with a voltage reference circuit ideal.

Voltage reference circuit ideal:

This is the output voltage should remain singer, even when the output load resistance varies in a fairly wide range and when the input voltage varies in a specific range. A circuit with Zener diode voltage.

To determine the input resistance (Ri) is considered (Ri limits the current through the Zener diode and the voltage V decreases). We can write: Ri = (V-Vz) / (Iz – IL); clearing I = (Iz + IL). Zener resistance is assumed ideal diode is zero. Iz = V – Vz / Ri) – IL. Where IL = Vz / Rl and variables are the input voltage source V and the load current IL. For proper operation of this circuit, the diode must remain in the breakdown region and in the provision of power diode and may not exceed its nominal value.

In other words.

* The diode current is minimal, Iz (min) when the load current is maximum, IL (max) and the source voltage is low, V (min).}

* The diode current is maximum, Iz (max) when the load current is minimum, Iz (min) and the source voltage is maximum, v (max). then we obtain:

Ri = [V (min) – Vz] / [Iz (min) + IL (max)]

Ri = [V (max) – Vz] / [Iz (max) + IL (min)]

Equating these two equations

[V (min) – Vz] x [Iz (max) + IL (min)] = [V (max) – Vz] / [Iz (min) + IL (max)]

Since there are two unknowns Iz (min) using the following equation:

Iz (max) = (IL (max) x [V (max) – Vz)] – IL (min) x [V (min) – 0.9 Vz – 0.1 V (max). eg

Design a voltage regulator using the circuit shown. Suppose the diod Zebner has a breakdown voltage Vz = 10V, the voltage source is in the range 20v


The maximum load current and minimum are:

IL (max) = Vz / RL (min) = 10 v / 100 = 100 mA

IL (min) = Vz / RL (max) = 10 V / 150 = 20 mA

Using the equation of Iz (max) we have:

Iz (max) = (IL (max) x [V (max) – (Vz)] – IL (min) x [V (min) – Vz) / V (min) – 0.9 -0.1 v Vz (max ). substituting the values:

Iz (max) = (100) x [V (24) – (10)] (20) x [(20) – 0.9 (10) – 0.1 (24)] = 140mA

The maximum power dissipation in the Zener diode is:

Pz (max) = Iz (max). Vz = (0.14). (10) = 1.4W

Then the following equations are chosen either:

Ri = [V (min) – Vz] / [Iz (min) + IL (max)]

Ri = [V (max) – Vz] / [Iz (max) + IL (min)]

Example: Let the clamp circuit that includes a separate voltage source Vb with a diode. Find the waveform output.


In this circuit we assume for simplicity that Vd = 0V (ideal) output level is shifted in Vb. Shows an input signal Vi (t) square wave signal and the resulting output voltage Vo. When the polarity of Vb is as shown, the output is shifted in a negative direction of voltage.

* Circuit b) Input and output square wave.


The bipolar junction transistor (BJT): It starts with a description of the basic structure of the transistor and a qualitative description of its operation. Be used for description of the basic concepts of PN junction diodes. The bipolar transistor (BJT) is formed by three doped regions separately.

Types of transistors: two transistor types NPN and PNP on.



A transistor equals unpolarized opposing diodes, each having a gate, where the three regions and their emitter terminals are demonizes (E), base (B) and collector (C), the flow of electron currents obtained through the different parts of the transistor.

Electron emitter:

Here is shown a polarized transistor, minus signs represent free electrons. The emitter is heavily doped its function is free electrons emit or inject the base. Lightly doped base toward the collector passes most of the electrons injected by the emitter. The collector is so called because it collects or gathers most of the electrons from the emitter basis. The collector is so called because it collects or gathers most of the electrons from the base.

Electrons in the database:

At the instant at which the forward bias is applied to the emitter diode. Electrons have not entered the emitter area of the base.

Field effect transistors (FET)

A bipolar junction transistor (BJT) is a current controlled device in which both the electron stream as the hole current. The field effect transistor (FET) is a unipolar device, operates as a voltage controlled device with either electron current in a N-channel FET or a hole current P-channel FET both types of FETs are controlled by a voltage between the gate and source.

The BJT or FET devices could be used to operate an amplifier circuit (or other similar electronic circuits). With different polarization considerations.


* It has an extremely high input resistance (about 100M).

* No union has a voltage when using switch (Switch).

* To some extent immune to radiation.

* It is less noisy.

* Can be operated to provide higher thermal stability.


To explain the low frequency transistor to have to explain what quadrupole. This is a circuit that communicates with the outside world only through ports of entry (IN) and output (OUT).

Quadrupole equations is given by:

V1 = H11I1 + H12V2

H21I1 + I2 = H22V2

Where V1 and I2 are dependent variables, while I2 and V2 are independent variables. The values of h11, h12, h21 and h22 are called hybrid parameters (h), because it has no dimensions homognicas.

Transistor hybrid model:

To reach the linear model in pure alternating current of a transistor or its equivalent circuit, we basically assume that variations around the operating point are small.

Polarization of JET and MOSFET:

Considering a power amplifier configuration – common (FC). Polarization methods are similar to the MOSFET.

FET AC Operation:

The AC equivalent circuit of the FET. Can now be used in the analysis of various FET amplifier configurations with respect to the voltage gain and the input and output resistances. The AC output voltage is:

As Vi = voltage gain of the circuit is:

The AC impedance in view of the amplifier is:

And the AC impedance seen from the load to the output terminal of the amplifier is:

Transfer characteristics:

Is a drain current curve as a function of gate voltage – strong, for a constant drain voltage – Strong. The transfer characteristic can be directly observed on a plot of curves, obtained by measuring the operation of the device, depicted in the drainage feature.

Field effect transistors

Fet Types:

The FET (Field Effect Transistor), JFET (transistor junction field effect) emptying. MOSFET (field effect transistor oxide semiconductor) emptying. Can be used to amplify small signals, variable in time. By comparing the FET with the BJT shows that the drain (D) is analogous to the collector, while the source (S) is analogous to the emitter. A third contact, the gate (G) is analogous to base.


Just as there BJT configurations, which exist for the JFET.

* (FC) Common source.

* (GC) common gate.

* (DC) common Drain


An amplifier system consists of a transducer signal collector, followed by a small signal amplifier, a signal amplifier and a large output transducer device. The input transducer signal is usually small enough to be amplified so that it can be used to operate a device health.

Voltage amplifiers provide a voltage signal large enough for the large signal amplification stages in order to operate output devices such as speakers and motors.

A large signal amplifier must operate efficiently and be able to handle large amounts of power (in watts).

The power amplifiers are classified according to the percentage of time the collector current is different from zero.

There are four main classifications: Class A, Class B, Class AB, Class C. This module discusses the first two.

Operating in Class A:

It was considered at the beginning of the transistors (BJT), where the amplifiers fully reproduce the input signal. The collector current is not zero all the time. This class is inefficient, because no input signal, there is one that is different from zero and the transistor dissipates power in static or resting conditions.

Power amplifier circuits in Class A:

In general, the power amplifier circuits containing transistors capable of handling high power. These normally operate at voltages greater than the low power transistors and thus often require a separate voltage source.

For example, the voltages of the power transistors can exceed 450 V. Current capabilities are often higher than 10th DC (DC). As these high power transistors need to dissipate, are designed differently from the low power transistors and may include circuitry for current limiting protection. Also considered as additional heat dissipation that occurs during operation.



Harbin Zambrano

Jomar Araque

Jorge Hernandez

Submitted by:

Douglas Alfredo Dominguez Ruiz

Bolivarian Republic of Venezuela

Ministry of Higher Education

Process Associate – Technology

Electronic Engineering